Fix bindings of trailing returns

src/parser/cxx/ast_rewriter.cc

@@ -2516,17 +2516,27 @@ auto ASTRewriter::ExpressionVisitor::operator()(LambdaExpressionAST* ast)
     lambdaSpecifierList = &(*lambdaSpecifierList)->next;
   }
 
-  copy->exceptionSpecifier = rewrite(ast->exceptionSpecifier);
+  {
+    auto _ = Binder::ScopeGuard(binder());
 
-  for (auto attributeList = &copy->attributeList;
-       auto node : ListView{ast->attributeList}) {
-    auto value = rewrite(node);
-    *attributeList = make_list_node(arena(), value);
-    attributeList = &(*attributeList)->next;
+    if (copy->parameterDeclarationClause) {
+      binder()->setScope(
+          copy->parameterDeclarationClause->functionParametersSymbol);
+    }
+
+    copy->exceptionSpecifier = rewrite(ast->exceptionSpecifier);
+
+    for (auto attributeList = &copy->attributeList;
+         auto node : ListView{ast->attributeList}) {
+      auto value = rewrite(node);
+      *attributeList = make_list_node(arena(), value);
+      attributeList = &(*attributeList)->next;
+    }
+
+    copy->trailingReturnType = rewrite(ast->trailingReturnType);
+    copy->requiresClause = rewrite(ast->requiresClause);
   }
 
-  copy->trailingReturnType = rewrite(ast->trailingReturnType);
-  copy->requiresClause = rewrite(ast->requiresClause);
   copy->statement = ast_cast<CompoundStatementAST>(rewrite(ast->statement));
   copy->captureDefault = ast->captureDefault;
   copy->symbol = ast->symbol;
@@ -3974,6 +3984,13 @@ auto ASTRewriter::DeclaratorChunkVisitor::operator()(
   copy->parameterDeclarationClause = rewrite(ast->parameterDeclarationClause);
   copy->rparenLoc = ast->rparenLoc;
 
+  auto _ = Binder::ScopeGuard{binder()};
+
+  if (copy->parameterDeclarationClause) {
+    binder()->setScope(
+        copy->parameterDeclarationClause->functionParametersSymbol);
+  }
+
   auto cvQualifierListCtx = DeclSpecs{rewriter()};
   for (auto cvQualifierList = &copy->cvQualifierList;
        auto node : ListView{ast->cvQualifierList}) {

src/parser/cxx/parser.cc

@@ -1138,6 +1138,8 @@ auto Parser::parse_lambda_expression(ExpressionAST*& yyast) -> bool {
       }
 
       expect(TokenKind::T_RPAREN, ast->rparenLoc);
+
+      setScope(ast->parameterDeclarationClause->functionParametersSymbol);
     }
 
     parse_optional_attribute_specifier_seq(ast->gnuAtributeList,
@@ -5452,6 +5454,8 @@ auto Parser::parse_function_declarator(FunctionDeclaratorChunkAST*& yyast,
     }
 
     if (!match(TokenKind::T_RPAREN, rparenLoc)) return false;
+
+    setScope(parameterDeclarationClause->functionParametersSymbol);
   }
 
   lookahead.commit();

tests/unit_tests/sema/trailing_return_type_02.cc

@@ -0,0 +1,11 @@
+// RUN: %cxx -verify -fcheck -dump-symbols %s | %filecheck %s
+
+auto f(int x) -> decltype(x);
+auto g(int x, decltype(x)* y) -> decltype(y);
+auto k(int x) -> decltype((x));
+
+// clang-format off
+//      CHECK:namespace
+// CHECK-NEXT: function int f(int)
+// CHECK-NEXT: function int* g(int, int*)
+// CHECK-NEXT: function int& k(int)